A typical method of forming a pattern over a semiconductor substrate is to utilize photolithographic processing to form a patterned mask of photoresist over the substrate. FIG. 1 shows a prior art construction 10 comprising a substrate 12 and several patterned blocks 14 of photoresist formed over substrate 12. The patterned blocks are separated from one another by gaps 15.
Substrate 12 can comprise, for example, a monocrystalline silicon wafer. To aid in interpretation of this disclosure and the claims that follow, the terms “semiconductive substrate” and “semiconductor substrate” are defined to mean any construction comprising semiconductive material, including, but not limited to, bulk semiconductive materials such as a semiconductive wafer (either alone or in assemblies comprising other materials thereon), and semiconductive material layers (either alone or in assemblies comprising other materials). The term “substrate” refers to any supporting structure, including, but not limited to, the semiconductive substrates described above.
Patterned blocks 14 can be formed by first providing a layer of photoresist across an entirety of an upper surface of substrate 12, exposing the photoresist to patterned actinic radiation which renders some portions of the photoresist more soluble in a developing solvent than other portions, and subsequently utilizing the developing solvent to remove portions of the photoresist and leave the blocks 14 of the resist remaining over substrate 12. The actinic radiation can be, for example, ultraviolet light. The developing solvent can be any appropriate fluid (typically liquid) utilized for developing a pattern in the photoresist after exposure of the photoresist to actinic radiation. The term “developing solvent” thus encompasses any developer solution, including dissolving agents, organic solvents, etc.
Photoresist blocks 14 define a mask, and such mask can be utilized for patterning underlying substrate 12. Specifically, the substrate 12 can be subjected to an etch while the patterned mask comprising blocks 14 protects various regions of substrate 12, and accordingly openings will be formed selectively in regions of substrate 12 which are not protected by one of the patterned blocks 14.
A continuing goal in semiconductor device processing is to decrease dimensions of devices, and thereby conserve valuable semiconductor substrate real estate. A minimum distance between adjacent blocks 14 is constrained by parameters utilized in the photolithographic process. Accordingly, various procedures have been developed which can reduce a dimension of a gap between adjacent features of a photoresist mask, and which can thereby be utilized to reduce the size of features patterned utilizing the mask. An exemplary process which can be utilized to reduce the size of a gap between adjacent features of a photoresist mask is described with reference to FIGS. 2 and 3.
Referring to FIG. 2, a material 16 is provided over and between the discrete blocks 14 of the patterned photoresist mask. Material 16 can comprise an AZ R composition available from Clariant International, Ltd, such as, for example, the compositions designated as AZ R200™, AZ R500™, and AZ R600™. Such composition can be spin coated across an entirety of the upper surface of a semiconductor wafer, and is shown coated across the entirety of fragment 10. The material is utilized with chemically-amplified resist, and specifically is utilized with resist having a photogenerated acid therein. The semiconductor wafer having material 16 thereover is baked at a temperature from about 100° C. to about 120° C. Such baking diffuses acid from resist 14 into the material 16, to form chemical crosslinks within portions of the material 16 that are proximate to the various masses 14. Such causes portions of material 16 in contact with resist blocks 14 to be selectively hardened relative to other portions of material 16 that are not sufficiently proximate to the resist blocks.
Referring to FIG. 3, material 16 is subjected to conditions which selectively remove the portions of the material which have not had chemical crosslinks formed therein, while leaving the material that is in contact with photoresist masses 14 (i.e., the portions which have had chemical crosslinks formed therein). Such removal can be accomplished by exposing fragment 10 to an appropriate solvent, such as, for example, 10% isopropyl alcohol in deionized water, or a solution marketed as “SOLUTION C™ by Clariant International, Ltd.
In applications in which AZ R200™, AZ R500™, or AZ R600™ is utilized, fragment 10 can be subjected to a so-called hard bake at a temperature of from about 100° C. to about 140° C. after removal of the non-crosslinked material. Such hard bake can fully dry and further crosslink the portions of material 16 remaining associated with photoresist blocks 14.
The material 16 remaining around blocks 14 increases a size of the features of the patterned mask. In other words, photoresist blocks 14 together with crosslinked material 16 form a patterned composition over substrate 12, with such composition having discrete masking features 18 separated by gaps 20. The gaps 20 are smaller than the gaps 15 that had originally been present between blocks 14 of FIG. 1. The smaller gaps 20 can enable smaller openings to be patterned into substrate 12 than could be patterned with the photoresist blocks 14 alone, which can enable fabrication of smaller circuit device components relative to the size of the components which would be formed utilizing photoresist blocks 14 alone.
The processing of FIGS. 2 and 3 can provide a significant improvement relative to processes which utilize photoresist alone. It would be desirable to develop further improvements of methodologies for forming patterned masking compositions, and in particular it would be desirable to develop improvements enabling selective control of the thickness associated with the features of a patterned masking composition.